Gaseous fuel injector having high heat tolerance

ABSTRACT

A high pressure gaseous fuel injector for injecting natural gas or other gaseous fuels at high pressures (eg. 300 to 700 psig more or less) into combustion engines for improved efficiency, better performance and reduced environmental emissions. The fuel injector is powered by hydraulic signals from an electrohydraulic valve. The fuel injector includes an outer cartridge housing and a universal valve cartridge mounted therein. The cartridge comprises an activator body and a valve body secured together, and the valve body has a gas valve slidable therein. The stroke of the valve is adjustable by controlling the size of shims in the valve body assembly, thereby providing a universal valve cartridge that can be easily adapted to differing fueling requirements for models and sizes of engines. The valve body includes a spring chamber between upper and lower valve guides. The valve body also includes cross-holes to allow cool gaseous fuel to successively pulsate into and out of the spring chamber and thereby cool the exposed portion of the valve between guides, preventing heating of the dynamic gas seal located in the upper guide. An unsealed small clearance between the actuating piston and its bore in the actuator body allows controlled leakage of oil. The leakage of oil lubricates metal to metal contact between the upper guide and the valve and lubricates the dynamic gas seal. Gaseous fuel leakage into the leaked oil is tolerated and any combined oil/gaseous fuel is removed to an external location for separation. Spring washers are used to urge the valve assembly insert against a metal O-ring supported by the outer cartridge body.

FIELD OF THE INVENTION

[0001] The present invention generally relates to fuel injectors, andmore particularly high pressure gaseous fuel injectors for internalcombustion engines.

BACKGROUND OF THE INVENTION

[0002] The natural gas transmission industry and chemical processindustries use a large number of large-bore, 2-stroke and 4-strokenatural gas engines for compressing natural gas. For example, industriesuse these engines for such purposes as maintaining pressure in theextensive network of natural gas pipelines that supply residentialhousing and commercial businesses. The network of natural gas pipelinestypically operate at high pressures in the neighborhood of between 500psig and 1000 psig.

[0003] These large-bore, natural gas engines may be powered by a smallportion of the natural gas passing through the pipelines. However,before being injected into the engine, the pressure of the gas issignificantly and substantially reduced. Gaseous fuel is typicallyinjected into these cylinders at low pressures (for example, 15 psig to60 psig by mechanically actuated fuel injectors, such as that disclosedin Fisher, U.S. Pat. No. 4,365,756. The problem with low pressureinjection is that the fuel pressure provides little kinetic energy withwhich to induce cylinder charge mixing. There is ample evidence that thefuel and air in these large bore engines are not well mixed and as suchexhibit poor combustion stability, high misfire rates and significantcycle-to-cycle variations in peak pressure. As a result, these enginesare not efficient and also are environmentally detrimental, contributingto approximately 10% of the total NO_(x) production in the United Statesfrom stationary combustion sources according to estimates.

[0004] The concept of using high pressure fuel delivery to enhance fuelmixing in these engines has been proposed as a means to improveefficiency and environmental emissions from these engines. However,retrofitting existing engines provides a significant hurdle becausethese engines are manufactured by different companies and also vary insize. Moreover, injecting fuel at high pressure as opposed to lowpressure requires the fuel injectors to operate under extremely highoperating pressures which in turn greatly increases stresses andpowering requirements for opening and closing the valves. A keyrequirement for any proposed high pressure fuel injector is reliability.These large-bore, natural gas engines typically run continuously overlong time periods, meaning that any suitable fuel injector must becapable of reliably enduring very long operating cycles of the engine.It is desirable for example, that the fuel injectors reliably operateover several hundred million continuous cycles of the engine (about oneto two years before replacement). As such, a valve must achievereliability over this long time period or operating interval. Fuelinjectors of the prior art such as that disclosed in Fisher, U.S. Pat.No. 4,365,756 are not capable of reliably sealing and accuratelycontrolling the injection of gas at high pressure. Only recently haveeconomic and environmental pressures on the gas industry resulted injustification for advances in fuel injection technology. For at leastthe foregoing reasons, commercial large bore 2-stroke and 4-strokenatural gas engines continue to be fueled at low pressure byconventional low pressure fuel injectors.

SUMMARY OF THE INVENTION

[0005] It is the general aim of the present invention to provide acommercially reliable and practical fuel injector for injecting highpressure gaseous fuel (eg. around 300-700 psi or more) into combustionengines.

[0006] It is an object of the present invention according to one aspectto provide a fuel injector that can withstand the forces of highpressure gaseous fuel and has a long service operation but does not leakeither gaseous fuel or hydraulic fluid to the external environment.

[0007] It is another object of the present invention according toanother aspect to provide a fuel injector that is universal in that thefuel injector assembly can be easily adapted without any or anysubstantial redesign to fit and operate as desired on the various typesand sizes of combustion engines in industry.

[0008] It is a another object of the present invention according toanother aspect to provide a highly reliable fuel injector, andspecifically one that is not susceptible to thermal damage from theengine.

[0009] It is another object to provide a fuel injector with increasedoperating life, whereby gas leakage, eventually expected from O-ringsand sliding gas seals, is captured and safely and properly disposed of,on an ongoing basis, not requiring engine shut-down to replace theinjector valve.

[0010] In accordance with these and other objectives, the presentinvention provides a fuel injector cartridge and a fuel injectorincorporating the same, that uses the relatively cool gaseous fuelpassing through the valve to directly cool the exposed surface of thevalve and therefore limit the amount of heat transferred from the enginecylinder to the gas seals. The fuel injector cartridge includes a valvebody having an outer sleeve, and upper and lower guide collars mountedin the sleeve. The stem of an elongate valve extends up into and throughthe guide collars for radial retention. The valve is slidable throughthe guide collars for linear reciprocating movement between open andclosed positions. The guide collars are separated by a cooling chamber(which in the preferred embodiment doubles as a spring chamber) in whicha portion of the valve stem is exposed. The sleeve has at least onecooling port (that takes the preferred form of a plurality ofcross-holes) that allows the cool gaseous fuel to pulsate into and outof the cooling chamber correspondingly as the valve opens and closes.During opening of the valve, gas pressure drops in the gas passageway,resulting in a suction effect sucking the now heated gas (by virtue ofdirect contact with the valve, spring and guides) out of the coolingchamber. During closing of the valve, the pressure increases in the gaspassageway forcing new more cool gaseous fuel into the cooling chamber.

[0011] It is an aspect of the present invention that the lower collarguide is a self lubricated high temperature graphite/carbon bushing. Abushing retainer is provided below the bushing to prevent any chipswhich may form from dropping into the outlet port.

[0012] It is another aspect of the present invention that a metal O-ringis used at the between the bottom of the cartridge and the cartridgehousing to provide a seal axially between the cartridge housing and thecartridge body. The metal O-ring can withstand the high temperaturesnearest to the cylinders of the engine and provide a highly reliablyseal at the same time. Means in the preferred form of load washersengage the other axial end of the valve housing to axially compress themetal O-ring. A force in the rough neighborhood of about 10,000 isnecessary to maintain a seal for high pressure fuel injection over about300 psi.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a cross-sectional view of a high pressure fuel injectorassembly in accordance with a preferred embodiment of the presentinvention, illustrated in a closed position.

[0014]FIG. 2 is a cross-sectional view of a high pressure fuel injectorassembly similar to that in FIG. 1 but in an open position.

[0015]FIG. 3 is an enlarged cross sectional view of a portion of thehigh pressure fuel injector illustrated in FIG. 1.

[0016]FIG. 4 is an enlarged cross sectional view of another portion ofthe high pressure fuel injector illustrated in FIG. 1.

[0017]FIG. 5 is an enlarged cross-sectional view of the high pressurefuel injector assembly of FIG. 1 but taken about a different plane toindicate the provision of the gas/oil outlet.

[0018]FIG. 6 is a schematic illustration of the high pressure fuelinjector assembly of FIG. 1 in an engine system environment.

[0019]FIG. 7 is a perspective and partly schematic illustration ofmultiple high pressure fuel injector assemblies in an engine systemenvironment and mounted to an engine.

[0020]FIG. 8 is a perspective view of the high pressure fuel injectorassembly of FIG. 1.

[0021]FIG. 9 is a perspective view of the high pressure fuel injectorassembly of FIG. 1, but with a different embodiment of the fuel injectorhousing.

[0022] While the invention will be described in connection with certainpreferred embodiments, there is no intent to limit it to thoseembodiments. On the contrary, the intent is to cover all alternatives,modifications and equivalents as included within the spirit and scope ofthe invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Referring to the cross section of FIG. 1, the present inventionis embodied in a high pressure fuel injector assembly 20. The highpressure fuel injector assembly 20 generally comprises a fuel injector22 and an electrohydraulic valve assembly 24. In general, theelectrohydraulic valve assembly 24 hydraulically operates the fuelinjector 22 to successively inject gaseous fuel such as natural gas intothe cylinders of an engine 121. A partly schematic illustration of anengine 121 with multiple fuel injector assemblies 20 is illustrated inFIG. 5. The disclosed fuel injector assembly 20 provides a commerciallyreliable and practical fuel injector for injecting high pressure gaseousfuel (eg. around 300-700 psig, but also including greater and lesserpressure) into combustion engines, thereby improving the efficiency ofthe engine and reducing the environmental emissions therefrom. Detailbelow will first be given to the structure and function of the highpressure fuel injector assembly 20 as shown in FIG. 1 and then to anexemplary engine operating environment for the assembly 20.

[0024] Although electrohydraulic valves are not believed to have beenpreviously applied to the present art, it should be noted thatelectrohydraulic valves and associated mounting assemblies are generallyknown in other related fields of art. As such, for purposes of thepresent invention, the electrohydraulic valve assembly 24 is intended tohave a broad meaning and may include an electrohydraulic valve 26, and amounting block 28 for mounting the electrohydraulic valve 26 to the fuelinjector cartridge 22. A mounting flange 30 secures the entire assembly20 to the engine 121 via conventional fasteners or bolts as shown inFIG. 7. In the preferred embodiment, the electrohydraulic valve 26includes an electrical driver 23 such as an on/off solenoid and athree-way control valve 25. The three way control valve 25 has a highpressure inlet 27 connected to a pressurized hydraulic supply of oil orother suitable hydraulic fluid and a low pressure outlet 29 connected toa lower pressure sump of oil. In response to external electrical pulsesor signals from the electronic engine control, the electrical driver 23switches the control valve 25 between two positions to successivelyconnect an output 31 alternatively to the high pressure inlet 27 and thelow pressure outlet 29. This provides successive hydraulic signals andalso alternates the direction of hydraulic flow between theelectrohydraulic valve 28 and the fuel injector cartridge 22. Asillustrated in FIG. 5, the mounting flange 30 may provide an externalgas inlet port 33 for connecting a fuel supply to the inlet of thecartridge and an external gas/oil outlet port 35 for connection to a gasoil separator, the function of which will be described in further detailbelow.

[0025] Many aspects of the present invention are directed toward thefuel injector 22 which is operated by any suitable form of hydraulicsignals of a hydraulic type fluid such as oil. Hydraulic actuationprovides sufficient force to actuate the valve 46 despite large opposingforces due to the high gaseous fuel pressures, friction, and mechanicalspring forces in the cartridge 34. The fuel injector 22 generallyincludes an outer tubular cartridge housing 32 and an fuel injectorcartridge 34 mounted therein. In the preferred embodiment, the cartridgehousing 32 includes a hollow and cylindrical body tube 36, a nose piece38, and a mounting flange 30, all brazed together, and a nozzle 40 pressfit into the nose piece 38. Although the nozzle 40 could be integrallyprovided by the nose piece 38, providing a separate nozzle 40 allows foreasy design modifications of the nozzle which can be suited to differentsizes or types of engines. The nozzle 40 regulates and optimizesdispersion and mixing of the gaseous fuel in the cylinders of the engineand as such improves environmental emissions and efficiency of theengine. In the preferred embodiment, one end of the cartridge housing 32is closed by the electrohydraulic valve assembly 24 and the other end ofthe outer housing 32 is closed by the combination of the nose piece 38and the end portion of the fuel injector cartridge 34. The cartridgehousing 32 contains a gas passageway 41 for communicating gaseous fuelfrom the gas inlet port 33 to the nozzle 40. In the preferredembodiment, the gas passageway 41 is a large annular chamber between thehousing 32 and the cartridge 34. The volume of this chamber 42 ismaximized to provide a large local reservoir. This large gas reservoirserves to maintain desirably high gas injection pressure throughout theinjection event.

[0026] The fuel injector cartridge 34 generally comprises a generallycylindrical cartridge body 42 that houses a cylindrical piston 44 and anelongate valve 46. In the preferred embodiment, the cartridge body 42 isgenerally of two piece construction, including a lower valve body 48 andan upper actuator body 50 screwed together via interfitting threads orotherwise secured together. The combination of the stationarycomponents, eg. the cartridge body 42 and the outer cartridge housing32, provide a stationary support housing that provides the gaspassageway 41 into the engine cylinder and supports the movingcomponents such as the piston 44 and valve 46. Although it will beappreciated that in alternative embodiments the support housing may beprovided by fewer or more components. The actuator body 50 defines acylindrical bore or control chamber 52 in which the piston 44 isslidably mounted for linear reciprocating movement. The control chamber52 is connected by a drilled passage 54, connector tube 56, and orificeplug 71 to the output 31 of the electrohydraulic valve 26 for receivinghydraulic operating signals. The end of the drilled passage 54 providesa hydraulic input for receipt of hydraulic signals.

[0027] The valve body 48 generally includes a steel body sleeve 58 andupper and lower spaced apart cylindrical collar guides 60, 62. In thepreferred embodiment, the upper guide 60 is a solid machined steelmember while the lower guide 62 is a self lubricating, high temperature,carbon/graphite bushing formed from a commercially available material.The lower guide 62 is press fit into the sleeve 58. One potentialproblem with use of carbon/graphite material is fragility and thesusceptibility to chipping at the edges. As such, a steel washer orother bushing retainer 63 is seated in a recess in the sleeve 58 belowthe graphite bushing. The bushing retainer 63 prevents graphite orcarbon chips from dropping down and potentially lodging between thevalve 46 and valve seating surface 70. The valve 46 is slidably mountedthrough axially aligned bores in the guides 60, 62 for linearreciprocating movement between open and closed positions. The guides 60,62 thus support and guide the linear reciprocating movement of the valve46. As illustrated, the end portion of the valve body 48 closes one endof the cartridge housing 32. The sleeve 58 defines a frusto-conicalvalve seat 68 surrounding an outlet orifice 70 that provides fordischarge of gaseous fuel into the cylinders of the engine. To ensurecorrect alignment of the valve seat 68 and the bore of the bottom guide62, the inner diameter of the conical seat 68 and the inner diameter ofthe bore in the guide 62 are simultaneously or sequentially precisionground, thereby assuring accurate alignment. This provides precisealignment of the valve with its seat, resulting in long seat life, lowgas leakage, and therefore more precise and accurate control over fuelinjection. The lower end portion of the valve body 48 also includescross holes 72 formed in the sleeve 58 and below the lower valve guide62 to extend the gas passageway 41 to the outlet orifice 70.

[0028] A helical compression spring 66 is mounted in a spring chamber 64between the sleeve 58 and the valve 46 (surrounding the valve 46). Thespring 66 biases the valve 46 to a closed position as shown in FIG. 1 inwhich an enlarged frusto-conical closure member 74 on the valve 46 isseated against the valve seat 68 along a circular contact. Preferably,the respective slope or angles of the mating conical surfaces betweenthe seat 68 and the closure member 74 are offset slightly by a degree ormore to ensure tight circular contact which prevents leakage of gaseousfuel into the cylinders of the engine. As shown in FIG. 3, the spring 66engages a disc shaped spring retainer 76 which is secured to the valve46 by keepers 78. The spring provides a large force sufficient toprevent the high pressures of the gaseous fuel from causing fuel leakageinto the engine's cylinder while the valve is closed. Although thespring 66 could be eliminated if a 4-way actuating valve was provided inthe electrohydraulic valve in which the piston would be configured to behydraulically actuated both ways to both open and closed positions byhigh pressure hydraulic signals, the spring 66 performs the necessaryfunction of a fail-safe, in that the spring 66 mechanically maintainsthe valve 46 in the closed position in the event of failure of theelectrohydraulic valve or the hydraulic pressure supply.

[0029] In the preferred embodiment, the valve 46 is a separate memberfrom the piston 44, but another embodiment of the present invention mayintegrally provide the two or otherwise connect the two together. Theseand other possibilities are intended to be covered by all of the claimsappended hereto. The piston 44 includes a reduced diameter nose 80 whichcontacts the top surface of the valve. Surrounding the nose 80 is aseating surface 82 which is adapted to engage the top surface of theupper valve guide 60 acting as a mechanical stop to control the strokeor maximum distance of linear movement of the valve 46, and thereby thefuel injection rate.

[0030] To open the valve 46, the piston 44 is actuated in response tohigh pressure hydraulic signals or pulses from the electrohydraulicvalve 26. High pressure hydraulic signals result by a connection betweenthe output 31 and the high pressure inlet 27. High pressure hydraulicsignals received in the control chamber 52 overpower the force of thespring and linearly actuate the valve 46 to an open position asillustrated in FIG. 2 in which the closure member 74 is lifted off ofthe valve seat 68 to allow passage of gas through the outlet orifice 70and into the corresponding cylinder of the engine.

[0031] As or after the valve 46 opens, the electrohydraulic valve 26ends the high pressure hydraulic signal and switches the connection tothe output 31 by connecting the output to the lower pressure outlet 29.The spring 66 automatically returns the valve 46 to the closed position,causing hydraulic oil in the control chamber to flow to the lowerpressure outlet 29.

[0032] The preferred embodiment also includes an orifice plug 71 locatedin the input passage regulating flow between the electrohydraulic valve26 and the control chamber 52. It is an advantage that the orifice plug71 is more restrictive one way and less restrictive the other way, suchthat the valve 46 moves more quickly from the closed position to theopen position than the movement from the open position to the closedposition. Because the orifice plug 71 is less restrictive in thedirection associated with valve opening, reduced fluid pressure isrequired to achieve acceptable valve opening velocity. Reduced fluidpressure has the advantage of lower hydraulic power consumption, reducedfluid heating, and less hydraulic system stress. Reduced closingvelocity reduces the impact and resulting wear between the valve seat 68and the closure member each time the valve 46 closes. To accomplish thisflow regulation, each side of the orifice plug 71 has a differentdischarge coefficient. In particular, the plug 71 includes a restrictionorifice 73 and a conical or otherwise chamfered surface 75 on one sideof the restriction orifice 73 and a substantially flat surface 77 on theother side of the restriction orifice 73. The restriction orifice 73determines the maximum speed of actuation by limiting hydraulic flow.The chamfered surface 75 directs the pressure of the hydraulic signalslike a nozzle and increase the amount of flow through the orifice 73.The substantially flat surface 77 does not direct the flow into theorifice 73 and acts as a barrier thereby reducing the amount of flowthrough the orifice 73. As a result, the valve 64 moves more quicklytowards the open position and more slowly towards the closed position.The force of the spring 66 is also selected to control the return rate.

[0033] In accordance with an aspect of the present invention relating topracticality and reliability of the fuel injector 22 and the entireassembly 20, a small controlled amount of hydraulic oil leakage isallowed past the piston 44 for collection in a collection chamber 83between the actuator body 50 and the valve body 48. In the preferredembodiment, the collection chamber 83 is provided by recesses in theactuator body 50 and mounting block 28. The piston 44 and its matingbore in actuator body 50 are made with hardened, wear resistantsurfaces. When lubricated by hydraulic oil, these sliding surfacesexhibit long cyclic life with negligible wear. Conventional slidingseals are commonly known to not provide the required cyclic life and aretherefore considered to be not satisfactory for sealing between thepiston 44 and its bore. It is therefore an advantage to avoid usingsliding seals, and to simply incorporate the lubricated, hardened, steelsurfaces. The lubricating oil leakage passing the piston 44 is limitedby the small annular clearance between the piston 44 and its matingbore. There are several other advantages of this leakage. Onesignificant advantage it that the leaked hydraulic oil lubricates thesliding movement between metal to metal contact surfaces between theinner bore of the upper guide 60 and the valve 46. This increases wearresistance and significantly prolongs the life of the components in thecartridge 34. Another advantage is that the oil lubricates and prolongsthe life of a gas seal 84 between the upper guide 60 and the valve 46.The leaked oil collected in the collection chamber 83 is directed via anoutlet in the form of an axial outlet passage 86 in the cartridge body42 that is connected to the gas/oil outlet port 35 for removal to anexternal location where gas and oil separation can occur. It should benoted that the leakage is controlled to be a very small flow rate.

[0034] The O-ring gasket 85 prevents gas leakage from the gas passageway41 to the collection chamber 83. The gas seal 84 prevents gaseous fuelleakage between the valve 46 and the upper guide 60. The gas seal 84 islocated at the far lower end of the upper guide 60 such that oillubricates all or substantially all of the contacting surfaces betweenthe upper guide 60 and the valve 46. When initially installed, the gasseal 84 and the O-ring gasket 85 provide zero leakage of gas from thegas passageway 41 (including spring chamber 64) to the collectionchamber 83. However, it will be appreciated that over the lifetime ofoperation (eg. during several hundred million operating cycles) wear canoccur, which in turn, may and often causes slow gaseous leakage past thegas seal 84. Indeed, the intense gas pressure exerted by the fuel (eg.typically around 300-700 psig) greatly increases the likelihood of suchleakage occurring. The provision of the collection chamber 83 provides afail safe, tolerates such leakage and vastly extends the operating lifefor the fuel injector cartridge 34, because small gas leakage is carriedaway to an acceptable disposal means. If it were not for this gasleakage disposal means, the engine would have to be stopped, and theleaking cartridge replaced, at the first sign of gas leakage past theseals.

[0035] A second collection chamber 87 is also provided at the otheraxial end of the passage 86, generally between the actuator body 50 andthe mounting block 28 of the electrohydraulic valve assembly 24. Anumber of O-ring gaskets 88-91 are provided in this general vicinity andserve to prevent leakage. Two connector tube O-rings 88, 89 between theconnector tube 56 and the actuator body 50 and the mounting block 28 ofthe electrohydraulic valve 26 prevent leakage of oil into the collectionchamber 87. However, the continuous and cyclic pulses of hydraulic oilthrough the connector tube 56 presents a possibility of oil leakageafter a long time period. As such, small amounts of oil leakage can beallowed or is tolerated as it is collected in the second collectionchamber 87. An O-ring 90 is also provided between the mounting flange 30and the actuator body 50 to prevent leakage of high pressure gaseousfuel from the gas passageway 41. However, a small amount of gas leakageis also tolerated at this location, in which gas would be collected inthe second collection chamber 87 for removal. The outer O-ring 91prevents leakage of oil and gas to the external environment. It will beappreciated that the oil and any combined oil/gas in the secondcollection chamber 87 is at relatively low pressure, much lower pressurethan either the high pressure gaseous fuel supply or the hydraulic oilat the high pressure inlet 27. As a result, little pressure and thusminimal forces are exerted on this gasket 91 thereby providing a highlyreliable seal at this location and avoiding leakage to the externalenvironment.

[0036] From the foregoing, it will be appreciated by those skilled inthe art that the first and second collection chambers 83, 87 eachprovide a fail-safe for oil leakage or gas leakage at several locationsand two separate means for tolerating leakage of oil and gas at leastone location in the fuel injector assembly and for removal of anyleakage of hydraulic fluid and gas from the fuel injector assembly.

[0037] In accordance with another aspect of the present inventionrelating to universality of the valve cartridge 22, a shim 92 is used tocontrol the maximum stroke or distance of reciprocating movement of thevalve 46. As shown in FIGS. 1 and 4, the upper guide 60 is compressedaxially between the actuator body 50 and a shoulder/recess 93 formed inthe valve body sleeve 58. A stop plate 100 and shim 92 are positionedaxially between the upper guide 60 and the shoulder/recess to controlthe amount that the upper guide 60 protrudes from the valve body 48 andthe resulting overall axial length of the valve body 48. Excess threadsin the two bodies 48, 50 are provided to accommodate variations in theirengagements due to different sizes of shims. A thicker shim 92 willincrease the protrusion of the upper guide 60 relative to the upper faceof the valve 46. As a result, the distance between the outer face of thepiston 44 and the face of the upper guide will be reduced, causing thestroke of the valve to be reduced. This in turn results in less gaseousfuel being injected into the cylinders of the engine during each cycle.A thinner shim 92 will increase the allowable stroke of the valve 46,resulting in more gaseous fuel being injected into the cylinders of theengine during each cycle. The selection of the shim 92 thickness allowsthe valve cartridge 22 to be easily adjusted for larger and smallertypes of engines which have different fueling requirements. Thus thepreferred embodiment provides a valve cartridge and fuel injector thatare universal for a variety of different engines. Using the shim 92,conventional opening distances for the valve closure member 74 of thepreferred embodiment can be conveniently adjusted over the range ofopening distance range desired for these types of engines. This is animportant advantage when considering that the fuel injector 22 is usedto retrofit existing engines which exist in a wide variety of models andsizes. Also as shown, the shim 92 and a stop plate 100 axially retainthe gas seal 84.

[0038] In accordance with another aspect of the present inventionrelating to cooling and reliability, openings in the form of cross-holes94 are drilled into the valve body sleeve 58 at radially spacedintervals. The cross-holes 94 allow the cool gaseous fuel entering thegas inlet 33 and flowing through the gas passageway 41 to cool theexposed surface of the valve 46 inside the spring chamber 64. Duringoperation, the nozzle 40 and closure member 74 are exposed to extremetemperatures inside the cylinder of the engine, eg. up to about 2000degrees Fahrenheit. In contrast, the conventional material of gas sealand other conventional material gaskets and spring materials start tothermally deteriorate at around 300-400 degrees Fahrenheit. By coolingthe exposed surface of the valve 46, life of the gaskets/seals andspring and therefore life of the cartridge 34 is prolonged. Duringoperation, the pressure in the gas passageway 41 rises and falls as thevalve 46 opens and closes. This in turn causes relatively cool gas topulsate into and out of the spring chamber vastly enhancing the coolingeffect achieved. These cross-holes 94 direct this gas flow towards thevalve and spring and improve the life span and reliability of thecartridge 34 by removing heat that would otherwise travel up the valveand spring, undesirably raising the operating temperature of the springand seals.

[0039] Still another function of the cross-holes 94 is to provide ameans of restraining the gas valve body 48 while tightening/looseningthe threaded joint joining the actuator body 50 and the gas valve body48. This is accomplished by engaging pins in the cross-holes 94 using aholding fixture designed for that purpose.

[0040] Another novel feature of the preferred embodiment is theprovision of a metal O-ring 95 for sealing the contacting surfacesbetween the cartridge housing 32 and the cartridge 34. The metal O-ringprovides a highly reliable seal in a location proximate the enginecylinders where the temperatures are extreme. It will be appreciatedthat current materials for other more conventional types of gasketswould likely fail from thermal damage in this type of environment. Tomaintain the metal O-ring 95 in sealing relationship, a large axialforce, eg. of about 10,000 pounds, is applied by a spring in the form oftwo Belleville load or spring washers 96 supported by the body of theelectrohydraulic valve 26 and engaging the other axial end of thecartridge 34. Specifically, the load washers 96 engage a load pad 97situated in the second collection chamber 87 and seated in a formedrecess in the actuator body 50. Shim 98 is interposed between the loadpad 97 and the recess in the actuator body 50. It should be noted thatthe thickness of the shim 98 is selected to maintain the desired forceon the metal O-ring 95. In particular, recalling that the thickness ofthe shim 92 is variable depending upon the fueling rate requirements ofthe intended engine, the thickness of the second shim 98 depends uponthe thickness of the first shim 92. The thicker the first shim 92, thethinner the second shim 98 is to thereby maintain the same force on themetal O-ring 97. The thickness of second shim 98 is also adjusted toachieve deflection of the load washers as required to generate thedesired metal O-ring clamping force, compensating for the effects ofmanufacturing tolerances in the parts. A threaded hole 99 is alsodrilled 180 degrees apart from the axial passage 54 to facilitateinsertion of screw which can then be used to lift the cartridge 34 outof the housing 32. Together, threaded hole 99 and passage 86,diametrically opposite each other in the face of actuator body 50,conveniently accommodate a common spanner wrench adapter to facilitatetightening/loosening the threaded joint connecting the actuator body 50and the valve body 48.

[0041] Because of the number of moving components and seals, the fuelinjector cartridge 34 is intended to have a lifespan of about one to twoyears. As such, the cartridge 34 is easily replaced by removing theelectrohydraulic valve assembly 24, and the various parts between theelectrohydraulic valve and the cartridge and pulling the cartridge 34from the cartridge housing 32. The electrohydraulic valve 26, cartridgehousing 32 and interposed parts can be reused with a new replacementfuel injector cartridge 34 and new metal O-ring 95.

[0042]FIGS. 6 and 7 illustrate one such high pressure fuel injectionsystem 120 incorporating the high pressure fuel injector assembly 20.The primary advantage of this type of system is that the fuel injector22 injects fuel at high pressures greatly increasing air and fuel mixingin the cylinders and thereby resulting in fewer harmful environmentalemissions and increasing engine efficiency. FIG. 6 illustrates thesystem 120 in schematic form with a single fuel injector valve assembly20 while FIG. 7 illustrates the system 120 on an engine 121 withmultiple valve assemblies 20, one for each cylinder of the engine 121.The system 120 includes a hydraulic pumping unit 122 for supplying highpressure hydraulic oil to the electrohydraulic valve 26 and anelectronic controller 124 for driving the electrical driver 23 viaelectrical signals on electrical line 123. The hydraulic pumping unit122 in this case is located remote from the engine cylinders and may beelectrically or pneumatically powered. The preferred embodimentillustrated in FIG. 7 is an engine driven pump 126, a low pressure sumpor reservoir 128, and a gas/oil separator 130. The pump 126 is adaptedto pump hydraulic oil from the reservoir 128 to the high pressure inlet27 of the electrohydraulic valve 26 via a high pressure hydraulic oilsupply line 132. The pressure in this line 132 may be in the roughneighborhood of around 800 psig. A low pressure hydraulic return line134 connects the low pressure outlet 29 with the reservoir 128. Thispressure in this line 134 may be in the rough neighborhood of about 45psig. A gas/oil return line 136 connects the gas/oil outlet port 35 tothe gas/oil separator 130. The gas/oil separator 130 allows any combinedgas and oil to sit for a sufficient time at which the gas separates andis exhausted via a gas vent 138 to a non-explosive location. A gaseousfuel supply 140 of a combustible gas is connected to the gas inlet 33 bya gas line 142 that may have a pressure in the neighborhood of betweenabout 300-700 psig, or other suitable lower or higher pressure. Otherassociated equipment includes a hydraulic oil filter 144 for keeping thehydraulic oil clean and a gas leakage indicator 146 for sensingexcessive gas leakage which could indicate hazardous conditions.

[0043] All of the references cited herein, including patents, patentapplications and publications are hereby incorporated in theirentireties by reference. While this invention has been described with anemphasis upon preferred embodiments, it will be obvious to those ofordinary skill in the art that variations of the preferred embodimentsmay be used and that it is intended that the invention may be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications encompassed within the spirit andthe scope of the invention as defined by the following claims.

What is claimed is:
 1. A fuel injector for injecting gaseous fuel intoan engine, comprising: a tubular cartridge housing; a valve body in thecartridge housing, including a sleeve, and upper and lower guide collarsin the sleeve, the upper and lower guide collars being spaced apart andseparated by a cooling chamber; a gas passageway generally between thecartridge housing and the valve body for communicating gaseous fuel tothe engine through an outlet port; an elongate valve retained by theguide collars, having an exposed surface in the cooling chamber, thevalve being slidable between open an closed positions to open an closethe outlet port, respectively; at least one cooling port defined in thesleeve adapted to communicate gaseous fuel into and out of the coolingchamber for cooling the exposed surface of the valve.
 2. The fuelinjector of claim 1 further comprising a spring in the cooling chamberbiasing the valve to the closed position.
 3. The fuel injector of claim2 further comprising an actuator body secured to the valve body, and apiston, the actuator body defining a control chamber containing thepiston, the piston being separate from the valve and contacting the endof the valve, the piston being operated by a hydraulic working fluid toactuate the valve to the open position against the action of the spring.4. The fuel injector of claim 1 further comprising: a metal O-ringaxially between the valve body and the cartridge housing; and means forurging the valve body axially against the tubular cartridge housing tocompress the metal O-ring therebetween and provide a seal between thetubular cartridge housing and the valve body.
 5. The fuel injector ofclaim 1 wherein the at least one cooling port comprises a plurality ofcross-holes radially about the sleeve.
 6. The fuel injector of claim 1wherein the valve includes a closure member adapted to open and closethe outlet port, the closure member being exposed to the cylinder of theengine and the thermal environment associated therewith, furthercomprising a gas seal retained by the upper guide, the gas seal having athermal limit substantially below the thermal environment of the closuremember, gaseous fuel adapted to pulsate into and out of the coolingchamber and provide sufficient cooling the exposed surface of the valveto prevent thermal deterioration of the gas seal.
 7. The fuel injectorof claim 1 wherein the lower guide collar is a self lubricated, hightemperature, graphite/carbon bushing, and further comprising a bushingretainer between the graphite/carbon bushing and the outlet portpreventing chips from the bushing from reaching the outlet port.
 8. Thefuel injector of claim 1 wherein the sleeve defines the outlet port atits axial end and a conical valve seat surrounding the outlet port, thesleeve further comprising cross-holes between the lower guide collar andthe outlet port communicating the gas passageway to the outlet port. 9.A fuel injector cartridge for insertion into a tubular cartridge housingfor injecting gaseous fuel into an engine, a gas passageway beingprovided generally between the valve housing and the cartridge body forcommunicating gaseous fuel to the engine through an outlet port, thecartridge comprising: a valve body including a sleeve, and upper andlower guide collars in the sleeve, the upper and lower guide collarsbeing spaced apart and separated by a cooling chamber; an elongate valveretained by the guide collars having an exposed surface in the coolingchamber, the valve being linearly movable between open an closedpositions to open an close the outlet port; and at least one coolingport defined in the sleeve adapted to communicate gaseous fuel into andout of the cooling chamber for cooling the exposed surface of the valve.10. The fuel injector cartridge of claim 9 further comprising a springin the cooling chamber biasing the valve to the closed position.
 11. Thefuel injector cartridge of claim 10 further comprising an actuator bodysecured to the valve body and a piston, the actuator body defining acontrol containing the piston, the piston being separate from the valveand contacting the end of the valve, the piston being operated by ahydraulic working fluid to actuate the valve to the open positionagainst the action of the spring.
 12. The fuel injector cartridge ofclaim 9 further comprising: a metal O-ring axially between the tubularcartridge body and the valve housing; and means for urging the valvehousing axially against the tubular cartridge body to compress the metalO-ring therebetween and provide a seal between the tubular cartridgebody and the valve housing.
 13. The fuel injector cartridge of claim 9wherein the at least one cooling port comprises a plurality ofcross-holes radially about the sleeve.
 14. The fuel injector cartridgeof claim 9 wherein the valve includes a closure member adapted to openand close the outlet port, the closure member being exposed to thecylinder of the engine and the thermal environment associated therewith,further comprising a gas seal associated with the upper guide, the gasseal having a thermal limit substantially below the thermal environmentof the closure member, gaseous fuel adapted to pulsate into and out ofthe cooling chamber in correspondence with the opening and closing ofthe valve and provide sufficient cooling the exposed surface of thevalve to prevent thermal deterioration of the gas seal.
 15. The fuelinjector cartridge of claim 9 wherein the lower guide collar is a selflubricated, high temperature, graphite/carbon bushing, and furthercomprising a bushing retainer between the graphite/carbon bushing andthe outlet port preventing chips from the bushing from reaching theoutlet port.
 16. The fuel injector cartridge of claim 9 wherein thesleeve defines the outlet port at its axial end and a conical valve seatsurrounding the outlet port, the sleeve further comprising cross-holesbetween the lower guide bushing and the outlet port communicating thegas passageway to the outlet port.
 17. A fuel injector for injectinggaseous fuel into an engine, comprising: a tubular cartridge housing; afuel injector cartridge inserted into the cartridge housing, thecartridge having a cartridge body, a gas passageway generally betweenthe cartridge body and the cartridge housing for communicating gaseousfuel to the engine through an outlet port; an elongate valve slidablyretained in the cartridge body, the valve being linearly movable betweenopen an closed positions to open an close the outlet port; a metalO-ring axially compressed between the tubular cartridge housing and thecartridge body; and means for urging the cartridge body axially againstthe tubular cartridge housing to compress the metal O-ring therebetweenand provide a seal between the tubular cartridge body and the valvehousing.
 18. The fuel injector valve cartridge of claim 17 wherein theurging means comprises at least one spring washer.
 19. The fuel injectorvalve cartridge of claim 17 wherein the cartridge body includes asleeve, and upper and lower guide collars in the sleeve, the upper andlower guide collars being spaced apart and separated by a coolingchamber, and further comprising at least one cooling port defined in thesleeve adapted to communicate gaseous fuel into and out of the coolingchamber for cooling the exposed surface of the valve.
 20. The fuelinjector valve cartridge of claim 17 wherein the gaseous fuel has apressure of at least about 300 psi and the urging means applies an axialforce of at least about 10,000 pounds.